A clearly well-prepared Obama campaign led the attack, launching a website within minutes of Mitt Romney’s official announcement that called the House Budget Committee chairman’s budget proposals a “sham.”

The website, “Mitt Romney-Paul Ryan: The Go Back Team,” cites five facts that voters “need to know” about Ryan.

“Paul Ryan’s top-down budget plan is a sham,” reads the first entry.

The Obama campaign by Saturday afternoon released its first TV ad, a 94-second spot titled “Mitt Romney and Paul Ryan: Back to the Failed Top-Down Policies.”

The Ryan announcement essentially puts the final chess piece in play for the upcoming GOP national convention. And Ryan will have a chance to square off directly against Vice President Joe Biden in an Oct. 11 debate at Centre College, in Danville, Ky.

Democrats, in their rapid-fire responses Saturday, seemed eager to draw attention to Ryan’s balanced-budget plan, which they said would increase taxes on the middle class so millionaires can continue to get tax cuts. They also said Ryan’s conservative views are “out of touch with most Americans’ values” and would move the country backward on civil rights and women’s health issues.

Ryan, a seven-term congressman, also wasted no time Saturday, attacking President Obama in his first speech after Romney had announced him as a running mate.

"No one disputes that President Obama inherited a difficult situation,” Ryan said at a Norfolk, Va., naval yard with the USS Wisconsin in the background. "Whatever the explanations, whatever the excuses, this is a record of failure."

Obama campaign manager Jim Messina said the Romney campaign will try to portray the 42-year-old Ryan as a fiscal conservative whose House GOP-approved budget is an earnest attempt to scale back government and reduce the federal deficit.

However, Messina warned that Ryan, with Romney’s support, will in fact try to “end Medicare as we know it and slash the investments we need to keep our economy growing the all while cutting taxes for those at the very top.”

He also said Romney “doubled down on his commitment to take our country back to the failed policies of the past.”

Leading Democrats used strikingly similar language in their first-round efforts to knock down Ryan.

Senate Majority Leader Harry Reid said the Ryan pick shows Romney has “doubled down on his commitment to gut Social Security and end Medicare as we know.”

Maryland Democratic Rep. Chris Van Hollen said the Ryan choice tells him “Mitt Romney is doubling down on an economic approach that helps people like Mitt Romney.”

Maryland Democratic Gov. Martin O’Malley, a faithful Obama campaign surrogate, said the Ryan pick brings to the Romney candidacy “a strong commitment to end Medicare as we know it.”

Ryan and Romney were greeted Saturday in Norfolk with chants of "USA, USA" from the energized crowd.

Ryan also accused the Obama team of being "more worried about their next election than they are about the next generation."

Ryan may continue pushing for a version of the budget proposal he reintroduced earlier this year. That proposal would overhaul Medicare and Medicaid and make other sweeping changes that Democrats have labeled as extreme. But Ryan has stuck by his proposal as the solution to an ever-growing deficit inflamed by out-of-control entitlement spending.

In a dose of the tough-love approach for which Ryan's has become known, he said: "We promise equal opportunity, not equal outcomes."

Romney called his new running mate a man of "steadiness" and "integrity" when introducing him. He also praised Ryan as an "intellectual leader" of the party who understands the toll the federal debt is taking on the country but is optimistic about the future.

"He doesn't demonize his opponents,” said Romney, who at a campaign stop Saturday afternoon in Ashland, Va., called for an end to campaign attacks ads.

Romney initially fumbled his introduction of Ryan. In the closing line of his remarks, he referred to Ryan as the "next president." Romney quickly returned to the podium to correct himself.

The announcement comes as some polls, including a recent Fox News survey, show Romney losing ground to Obama.